US2117829A - Construction of gasometer roof tanks - Google Patents

Description

May 17, 1938.

E. H. STABER CONSTRUCTION OF GASOMETER ROOF TANKS Original Filed Jan. 26, 1934 INVENTOR 46 M v, 4 I I I TORNEY Patented May 17, 1938 UNITED STATES PATENT OFFICE Ernest H. Staber, New York, N. Y., assignor to Socony-Vacuum Oil Company, Incorporated,

New York, N. Y., a corporation of New York Original application January 26, 1934, Serial No. 708,351. Divided and this application August 18, 1936, Serial No. 96,687

1 Claim.

This invention is directed to improvements in storage tanks for volatile liquids, and more particularly, is directed to improvements in tanks having a gasometer type roof.

The gasometer roof tank is a tank in which the roof has a depending skirt which dips into a trough extending around the circumference of the tank wall proper, either inside or outside, at the top. This trough or well is fllled with liquid, and the tank roof is free to rise and sink in accordance with the vapor pressure below. The application of excess pressure and vacuum is avoided by the use of proper relief valves.

Pressure and vacuum relief valves'of the type commonly supplied have not been properly applicable to the problems presented by gasometer roof tanks.

An object of this invention is .to provide a suitable relief valve for vacuum and pressure relief for use in connection with such tanks.

The various objects and, advantages are obtained by means of the designs set forth in this specification and shown in the drawing attached to and made a part hereof.

Figure 1 of this drawing shows a vertical seci tion through the relief valves, and

Figure 2 shows a partial horizontal section taken at line 1-1 in Figure 1.

\ To protect the tank against vacuum and .against pressures which might not be properly reilieved due to failure of operation of the roof, or

0 other causes, I make use of protective vacuum and pressure relief valves which are set forth diagrammatically in Figure 1. In this figure,

i represents a tank, having a gasometer type roof,

formed by a top 9 and a skirt 8 dipping into a liquid well 3-4, 28 and 29 are valve chambers cylindrical in cross section, set up adjacent the top of the tank wall in a convenient operating location, and at a height such that they may communicate with each other through connection 30 and with the dip ring trap on the tank wall through connection 3i, thereby being filled with the same liquid as is used in the dip ring and being subjected automatically to the same conditions of dip ring level, etc. Chamber 28 is used for the release of pressure within the tank and is equipped with a vapor inlet 32 opening centrally into the bottom of the chamber 28. This vapor ing upward within chamber 28 to a level somewhat greater than the level of the water overflow on the dipring trap. Over this central pipe A 33 and surrounding it, there is placed a gasometer float 34 which extends in its normal position into inlet is surrounded by a circular pipe 33 extend the liquid in the vessel 28 to a depth of say 22 to 24 inches. This gasometer float 34 is made of a light weight metal such as aluminum and its weight is adjusted by machining so that it will rise and vent at the proper pressure. In other words; if the dip ring vent is designed to operate at say 3 inches of water and it is decided that the safety vent shall operate at flve inches of water, the weight of the gasometer float 34 is such that a pressure of five inches of water exerted upon its area will lift it, allowing gas to escape under the bottom of its skirt. In the design of valves for use on tanks working at high pressure, heavier metals, such as steel might be used. The skirt of this gasometer float 34 is provided with a plurality of ribs 35 which serve to guide it within chamber 28. Chamber 28 is open to the atmosphere through an orifice 31 at its top, and is of sufficient height to handle the full rise of gasometer float 34 and still retain it in position to properly return to its seat when through venting. Chamber 28 is connected to the pressure space within the tank by inlet 32 previously mentioned, and by pipe 38 which terminates within the tank at a point well up in the vapor space near the roof. For the relief of vacuum, a similar chamber 29, equipped with a similar interior pipe 39 and a similar gasometer float 40, is used, with the difference that in this case the port 4| at the bottom of chamber 29 is open to the atmosphere, and the top of the chamber 28 is closed to the atmosphere and in communication with vent line 38. The gasometer float 40 has similar ribs 36 and in this case is machined so that its weight enables it to act at the desired vacuum, which may for example be 1 of water, so that when a vacuum greater than this amount exists within the tank, the gasometer float 48 will rise and air admitted through 4| will pass upward through pipe 39, the gasometer float will rise to operating position, and the air will then pass downward around gasometer float 40-, into chamber 29, and through pipe 38 into the vapor space of the tank. It is noted that this type of construction provides an unusually long liquid seal. Any of the usual devices for protecting a vent line against the striking back will at once be apparent. In the past, relief valves of this type have been made so that they vented with a comparatively short rise and the rapidity with which they acted resulted in a considerable blowing of the sealing liquid. Many liquids have been used as seals ranging from mercury through glycerine to water and light petroleum fractions. None of them have been eminently successful, yet a liquid seal valve is so much more desirable than one sealed by mechanical seating of the valve, that the type has persisted in spite of its defects. These disadvantages 'I have avoided in several ways: First, I have eliminated the most frequently performed function, namely, that of pressure venting for ordinary rises, and do not call upon the vent valve to perform this routine venting, and reserve for it only the duty of emergency relief, which can only occur when excessive binding takes place between roof guides and rolls, (which condition should be immediately corrected). Secondly, I have provided a vent valve on the gasometer principle, having a depth comparatively great in relation to the necessary movement of the valve. For instance, in thepressure valve of the example cited, I have a 22 inch depth of seal to handle a five inch pressure variation, and consequently considerable blowing may take place before the liquid has been reduced to a depth where it will fail to seal. Third, I may so place these liquid seals that they are always in communication with and in a position to be replenished by the enormously larger reservoir of liquid in the dip ring seal, thereby assuring an ample supply-of liquid in seals of valves.

This case is a division of my copending application, Serial No. 708,351, filed January 26, 1934.

I claim:

In cooperation with a tank having a gasometer type roof, a pressure relief 'valve and a vacuum relief valve, each comprising a liquid seal in open communication with the roof seal of the tank, and in each seal a gasometer float valve, each valve of a predetermined weight to enable the preselected pressure variation to cause it to rise and vent, each valve having a skirt of relatively great length compared to the difference in sealing liquid levels at its venting position.

ERNEST H. STABER.

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